This invention relates to the field of nail polish compositions comprising film forming material, organic solvent, and clay thixotropic agent and methods of making such compositions.
Nail polish for coating human finger and toe nails typically comprises a film forming material such as nitrocellulose, organic solvent such as ethyl acetate, butyl acetate, toluene, and xylene, pigment for color, and clay as a thixotropic agent to provide thickening and prevent settling of pigment. Among the clays which have been used in the art are smectite, organophilic smectite, hectorite, bentonite, mica, montmorillonite, beidellites, saponites, vermiculites, stevensites, laponites, attapulgites, and others. The clays are usually modified with a quaternary amine, imidazoline, amine soap, fatty sulfate, sulfonates, and/or other organic compounds. For example, organically modified hectorite clay is known to be useful for suspending pigment in such nail polish compositions.
During the manufacture of such nail polish a gel of clay, solvent, and film forming material is formed and is then let down into a solvent and film forming material solution. The gel is conventionally subjected to homogination, also known as milling, to reduce the particle size of the clay by breaking up the clay. Typical homoginizers are sold under the brand names Dyno-mill and Gaulins. During the homogination step viscosity is built up over a residence time prior to the let down step.
The homogination/milling step is usually followed by several days or weeks of aging to reach acceptable viscosity prior to the let down step. These periods of time are problematic in high volume manufacturing processes and it has been an object in this art to improve nail polish manufacturing processes by reducing the residence time and aging time for this step.
Pigmented and unpigmented nail polishes are well known. In the case of pigmented nail polishes, pigment is usually added as a paste after the let down step.